Legacy LED light bulbs and fixtures use blue-emitting diodes in combination with phosphors or other wavelength-converting materials emitting red, and/or green, and/or yellow light. The combination of blue emitting LEDs and red-emitting and green- and/or yellow-emitting materials is intended to aggregate to provide a spectrum of wavelengths, which spectrum is perceived by a human as white light. However, although the resulting spectrum is intended to be perceived by a human as white light, many human subjects report that the light is significantly color-shifted. The reported color shifting makes such legacy LED lamps and fixtures inappropriate for various applications. Various attempts to improve upon legacy techniques have proven ineffective and/or inefficient.
Further, uses of green- and/or yellow-emitting materials in the exterior structure of a lamp that can be seen by a user are often regarded as undesirable, especially because the aesthetics of interior lighting has traditionally been based on a white or near-white exterior structure (e.g., as in the case of a legacy, incandescent, “Edison” bulb).
In some legacy LED lamps, blue LEDs are used in conjunction with down-converting phosphors embedded in an encapsulant, which encapsulant is disposed directly atop or in close proximity to the violet LEDs. However short wavelength light (e.g., blue light) is known to degrade the materials used in encapsulants, thus limiting the useful lifetime of the lamp.